When power supply wires are arranged in a semiconductor integrated circuit, wires for VDD and wires for VSS are arranged in each routing layer, and wires in different routing layers are connected to each other by via plugs. In this case, if the power supply wires and the via plugs occupy many routing tracks in each routing layer, signal wire efficiency becomes lower. On the other hand, if the number of the power supply wires and the number of the via plugs are simply reduced in order to prevent the signal wire efficiency from becoming lower, a drop of the power supply voltage becomes larger.